270 AVERS. [Vol. VI. 



Nevertheless there are observers who will not admit that 

 such can be the function of the basilar membrane, e.g. Paul 

 Meyer, who calls attention that among the lower vertebrates, — 

 viz. among the Reptilia, — the basilar membrane has the struc- 

 ture of a homogeneous plate ; and besides, the membrane is too 

 thick and not elastic enough among the Mammalia to serve the 

 purposes intended. According to Meyer, the hairs alone per- 

 form this function. 



If this was correct, it was argued that it would be impossible 

 to account for the formation of the basilar membrane. Keeping 

 the gradual development of the auditory sense in mind, it follows 

 that we must look for greater perfection of the anatomical basis, 

 for the two must go hand in hand. Most of the perfecting 

 changes have taken place in the cochlea. The arch of Corti 

 appears first among mammals, and the second row of strings 

 as well as the fourth row of hair cells, and perhaps many other 

 things which have remained undiscovered. The hair covering 

 of these cells is very different from what is fowid among lozver 

 vertebrates (the same is true of the auditory hairs of the rest of 

 the canal complex). When one remembers that in such animals 

 (fishes. Amphibia, and in part also birds), in contradistinction to 

 the weak development of the basilar membrane, the hairs show a 

 very prominent development {e.g. cupula terminalis, etc.), when 

 we consider all these things, Meyer's objections are satisfied, 

 and furthermore, it is not too much to hold that the basilar mem- 

 brane and auditory hair cells imdergo reverse processes of givzvth 

 and are perhaps dependent upon each other to a certain extent. 



But what is the significance of the hairs in the auditory appa- 

 ratus as a whole, and specially in the cochlea .'' 



Considered in organic continuity with their bearers, the cells, 

 they can hardly be separated from the latter in their significance 

 as percipient elements ; but in the case of the cochlea, where 

 only bars — bacilli, and no hairs in tJie proper sense — are pres- 

 ejit, it is necessary to limit the amount of their sensitiveness to 

 sound waves. One is forced to conclude that owing to their 

 unusual shortness and relative thickness they are scarcely 

 capable of regular vibrations. Helmholtz assumed that struc- 

 tures strongly damped would be relatively more strongly affected 

 by blows of short periods and streamings of the endolymph 

 than by musical tones. 



